The present invention relates to a magnetic valve.
More particularly, it relates to a magnetic valve which has a valve member which cooperates with the valve opening for closing and releasing the same, and an actuating element displaceable in a valve chamber for actuating the valve member, a permanent magnet arranged in the actuating member for holding the same in the end positions, and an electromagnet for producing a magnetic force displacing the actuating element between the respective positions.
The magnetic valves of the above mentioned general type are known in the art. One of the magnetic valves of this type, so-called bistable magnetic valve is disclosed in the German reference DE 4,000,071 A1. In this document the actuating element and the valve member are accommodated in a valve piston assembled from the centrally arranged disc-shaped permanent magnet, two soft iron rings abutting against the surfaces of the permanent magnet and having central openings filled with elastomeric filling pieces, and a sleeve-shaped guiding cage which surrounds the permanent magnet and the soft iron rings and holds them non-displaceably. The end abutments are formed by ferromagnetic connecting pieces which are arranged coaxially at both sides of the valve piston at a distance from it. The connecting pieces have central connecting openings with mouths which form in the valve chamber the valve openings of the magnetic valve. The end sides of the connecting pieces which face the valve piston are formed as valve seats which cooperate with the filling pieces in the soft iron rings for closing and releasing the valve openings. The guiding cage projects at one side beyond the soft iron rings so that it slides in each displacement position of the valve piston on the closing pieces which are outwardly provided with the guiding surfaces. The valve piston extends during its displacement movement through a circular opening in the central leg of the magnet core. With the exact coaxial orientation of the connecting pieces, the ring gap between the central leg and the valve pieces can be retained very small.
One of the valve openings controlled by the valve piston is provided for connection with a pressure source and the other valve opening is provided for connection with a pressure sink. The guiding cage further carries a ring collar arranged near the respective cage end and having a valve opening connectable with the pressure sink. This ring collar serves for supporting a pressure spring. The other end of the pressure spring abuts against the connecting piece which has this valve opening and in the abutment position of the valve piston closing this valve opening provides a prestress in the opening direction. The pressure spring is dimensioned so that the prestressing force of the valve piston which is held by the permanent magnet in the abutting or closing position cannot be displaced. This pressure spring serves for increasing the response sensitivity of the magnetic valve when the valve piston must be transferred to its another abutment position. It compensates the forces which is applied by the pressure of the medium flowing in the valve chamber from the pressure source and applied to the valve piston.